Wood preservation



Patented May 15, 1928.

UNITED STATES PATENT OFFICE WOOD PRESERVATION.

No Drawing. Application filed July 25, 1924, Serial No. 728,166. Renewed April 12, 1927.

A further object of this invention is to provide a material which will form either by oxidation, or by combination with an organic constituent of the wood or by both oxidation and combination a product which is toxic to wood boring organisms and which will be soluble in water, at the temperatures to which the wood is exposed, slightly in excess of the minimum toxic concentration for these organisms. By providing a material of this degree of solubility the toxic material is kept within the zone where it is to perform effective service for a prolonged period of time while at the same time a suflicient amount of the material is leached from the wood and dissolved so as to maintain an effective toxic concentration.

Other, further and more specific objectsof this invention will become readily apparent to persons skilled in the art from a consideration of the following description.

In applying preservative material to wood, in order to allow the impregnating material to penetrate the wood, air and moisture contained in the wood is wholly or in part removed by a preliminary treatment. This allows the preservative to either coat the wood fibres or the impregnation may be carried on so as to completely fill the pores. portion of the original moisture. of the wood may be removed either by seasoning or air drying and the actual impregnation accomplished by using any of the standard processes employing heat, pressure or vacuum or a combination of two' or more of these agents.

In carrying out my invention, I employ as the impregnating medium an organic compound which upon oxidation or upon chemical, physical or physico-chemical combination with one or more of the organic constituents of the wood or else by both oxidation and combination forms a compound which is toxic to wood boring organisms and also possesses a solubility in cold water slightly in excess of the minimum toxic concentration for the organisms. It is to be understood that the solubility of the toxic agent in the water will increase with rise in temperature, but in order that it may be effective under all conditions to which it is exposed while in use, it is essential that its solubility under the least favorable conditions, that is when in cold water, should be suflicient to provide a toxic zone of sufiicient concentration for effective action upon the organisms. I have tound, however, that such concentration at the low temperatures need not materially exceed that necessary to produce the minimum toxic concentration for the organisms, and by preserving the wood with a toxic material of this degree of solubility, I obtain great economy in the use of the toxic agent without sacrifice in rotection necessary for the treated woo The wood so treated is therefore protected by a preservative for a considerable period of time, for as long as the toxic material is present in the wood the wood boring organlsms will noteffectively attack the wood.

I have found that certain organic dyes are very effective for treating piling WhlCh is to be exposed in sea water to the action of marine organisms. Examples of these organic dyes are crystal violet, chrysoidine and malachite green. In using these dyes they are first dissolved in water, preferably hot water, so as to give a concentration of 1 to 5% and then the wood is impregnated therewith. When these dyes oxidize or combine with a constituent of the wood, for example, cellulose, lignin, tannin, etc., or if an oxidation product results from the combination of an organic constituent of the wood with A the dye, there is formed a compound possess ing lethal. ,properties against marine borers, the compound being very slightly soluble in sea water so that for a considerable number of years the treated piling may be kept in sea water and a sufiicient amount of the toxic agent will be continuously leached from the piling so that there will always be a zone of toxic concentration at the surface of the pile for action upon themarine borers and prevent efl'ective attack by such borers.

In order to assist in the formation of certain toxic agents of the desired solubility, I have found it advantageous under certain conditions to first mordant the wood. A

v fixative may also be used. A large number 'more or less evacuated pores by means of pressure.

, In addition to dyes of the classes heretofore named, I may use paraphenylenediamine, metaphenylenediamine, p-amidophen01, and similar compounds. These are employed in slightly ammoniacal solution and are fixed in the wood by oxidation with hydrogen peroxide or other oxidizer.

With oak piling certain dyes, such as the basic dyes, forv example, malachite green, Bismark brown, rhodamine, auromine, fast black, Victoria blue, chrysoidine, magenta, etc., may be used without mordanting the wood since there is suificient'tannin in the wood for fixing the dye, and compounds which ordinarily require the use of a mordant when treating pine or Douglas fir combine directly with oak wood to form a toxic compound. y

The amount of dye solution necessary for protecting timber from the attack of marine borers will vary from to 5% of the weight of the impregnated portion of the wood, depending largely upon the location of the marine structure. The intensity of attack by the marine borers depends upon the length of the breeding season for the borers. This breeding takes place only during the warm weather, and when the water becomes cold it is not necessary that there should be much solution of the toxic in the water. Hence, where the piling is placed in ,warmer climates, the ratio of impregnant to the treated wood should be greater than in the colder localities.

In treating pine or Douglas fir by my process, the wood is subjected to a preliminary impregnation with a mordant, for example a 2% tannic acid solution and then impregnated with a basic dye, such a 1% .solution of malachite green. In using this dye I prefer to employ a fixative, for example an acetate of copper or iron although other salts of copper, iron or aluminum have been found satisfactory for this purpose.

The fixative assists in the mordanting of the dye-with the tannic acid and is preferably added to the malachite green solution before the wood is treated therewith.

A very economical advantage of employing my invention consists in the fact that practically all of the toxic may be utilized in the treatment of the wood since these or ganic materials also possess the property of 'the dye bath being able to exhaust itself and The present invention is not limited to the alnples which should be construed as illus trative and not by way of limitation, and in view of the numerous modifications which may be efiected therein without departing from the spirit and scope of this invention, it is desired that only such limitations be imposed as are indicated in the appended claims.

I claim as my invention.

1. As an article of manufacture, wood impregnatedwith a combination product of a water soluble dye-stuff and an organic constituent of the wood, said product being toxic to wood-boring organisms and having a solubility in cold water slightly in excess of the minimum toxic concentration forsaid organisms.

2. As an article of manufacture, wood impregnated with a combination product of a Water soluble triphenyl methane dye-stuff and an organic constituent of the wood.

3. As an article of manufacture, wood impregnated with a combination product of the dye crystal violet and an organic constituent of the wood.

4. As an article of manufacture, wood impregnated with a combination product of a water soluble dye-stufi and an organic conspecific details set forth in the foregoing ex- 180 stituent of the wood, said product being a toxic to wood boring organisms and having a solubility in water at the temperautre to which the wood is exposed and slightly in excess of the minimum toxic concentration for said organisms.

HAROLD W. WALKER. v 

